When a foreign object (such as an implant) is introduced into a living (e.g. human or animal) body, i.e. in contact with the tissue therein, the body will react thereto. Typically the body will react by trying to reject the object by expelling it. If this is not possible the object is instead encapsulated in connective tissue so as to “exclude” it from the body.
The actual reaction or response obtained will depend on where in the body the object is introduced. Also, the manner of introducing the foreign object and the degree of damage that is inflicted upon the subject (human or animal), caused by the procedure itself will have an impact.
Furthermore, the material that the object is made of and the residence time of the foreign object in the body will be of importance for the reaction that is developed.
Many types of implants have been developed in the medical science, e.g. substitutes for bone such as titanium joints. Titanium is known to be very biocompatible in that it does not cause rejection reactions. It also has the property of easily being incorporated in the surrounding skeletal tissue in a desirable manner.
However, for certain types of implants rather the opposite is desirable, namely that the implant should not be incorporated into the surrounding tissue, and should absolutely not allow connective tissue to adhere thereto. One example is breast (or mammary) implants.
There are several different types of prior art breast implant. A common type is a silicon pad formed to the desired shape and consistency, as exemplified by U.S. Pat. No. 5,632,774 (Babian). Another common type is based on saline, sometimes also including solid filler materials such as silicon beads, enclosed in a bag or pouch. An example is disclosed in U.S. Pat. No. 5,554,671 (Waybreight et al). There are numerous other types based on combinations of these and other types of implant.
In the prior art there are disclosures of various methods of modifying the surface of such bags or pouches in order to increase their bio-compatibility for reducing or eliminating the encapsulation effect mentioned above. Such surface modification can be to physically treat the surface to modify the surface structure or chemically by binding chemical entities to the surface to provide a more bio-compatible surface.
In EP 0 696 210 (le Pesteur et al) there is disclosed the use of hydrogels based on hyaluronic acid and/or polydeoxiribonucleotides as materials for filling prostheses.
In US application No. 2002/0193448 A1 (Wallace et al) there is disclosed use of fragmented polymeric compositions, in particular hydrogels of proteins, polysaccharides or non-biological polymers, for e.g. controlled release of drugs.
None of the prior art documents known to the inventors address the issue of protecting an implant inside the body from being rejected or encapsulated or coated by connective tissue by providing an implant exhibiting a protective layer of bio-compatible material exposed on and/or through the surface of the implant, that is sustained over time and/or continuously renewed over time, so as to prevent and/or inhibit on-growth by cells, such as connective tissue. In fact, it is a well established notion that implants should not be allowed to “bleed”, i.e. leakage should not be allowed at all.